\begin{tikzpicture}[scale=2]
  \draw[->] (0,0) -- (-1.5,0) node[at end, above] {$y$};
  \draw[->] (0,0) -- (0,1.5) node[at end, above] {$z$};
  \draw[->] (0,0) -- (1/2., -1.73/2.) node[at end, above] {$x$};
\end{tikzpicture}
